1. Field of the Invention
The present invention relates to a portable display device, and more particularly to a portable display device having improved light leakage prevention.
2. Discussion of Related Art
Recently, various flat panel display devices have been developed having reduced weight and size. Exemplary flat panel display devices include a liquid crystal display, a field emission display, a plasma display panel, a light emitting display, etc.
Particularly, liquid crystal displays have become popular as an alternative to cathode ray tubes due to the liquid crystal displays' small size, light weight, and low power consumption. Such devices may be used in large-sized monitors and televisions as well as mobile phones and personal digital assistants (PDAs).
FIG. 1 is a exploded prospective view of a conventional portable display device. FIG. 1 shows a dual display device used in a mobile phone and the like and mounted with at least one liquid crystal display. FIG. 2 is an assembled sectional view taken along line A-A′ of FIG. 1.
Referring to FIGS. 1 and 2, the conventional portable display device 60 includes a liquid crystal display panel 4, a backlight assembly 50, a bottom chassis 22, a first printed circuit board 24, a second printed circuit board 26, and a light-emitting display panel 30.
The liquid crystal display panel 4, displays predetermined images using a first substrate 4a, a second substrate 4b and a liquid crystal (not shown) injected between the first substrate 4a and the second substrate 4b. 
The second substrate 4b includes a plurality of thin film transistors (TFT) arranged in matrix form. A source electrode of the TFT is connected to a data line, and a gate electrode thereof is connected to a scan line. A drain electrode of the TFT is connected to a pixel electrode made of transparent indium tin oxide (ITO), a conductive material. The TFTs are turned on when the scan line is supplied with a scan signal, and the TFTs supply a data signal from the data line to the pixel electrode.
An integrated circuit 6 is inserted on one side of the second substrate 4b, and the data signal and scan signal are supplied from the integrated circuit 6. A protective layer 8 is deposited around the integrated circuit 6.
The first substrate 4a is arranged facing the second substrate 4b. A common electrode made of ITO is deposited on the front surface of the first substrate 4a. The common electrode is applied with a predetermined voltage, and accordingly a predetermined electric field is generated between the common electrode and the pixel electrode. The array angle of the liquid crystal injected between the first substrate 4a and the second substrate 4b varies with the electric field, and the optical transparency also varies according to array angle to thereby display desired images. Upper and lower polarized light films (not shown) are provided in the upper and lower sides of the liquid crystal display panel 4.
The backlight assembly 50 includes a mold frame 16, LEDs 12, an LED substrate 14, a light guide plate 18, a reflective plate 20 and optical sheets 10.
The LEDs 12 emit an amount of light corresponding to a drive signal from the LED substrate 14. The light guide plate 18 supplies the light from the LEDs 12 to the liquid crystal display panel 4. That is, the light guide plate 18 supplies the light from its side surface to the liquid crystal display panel 4 located on its upper side.
The reflective plate 20 arranged on a back surface of the light guide plate 18 supplies incidence light from the light guide plate 18 back to the light guide plate 18. The optical sheets 10 enhance the brightness of light from the light guide plate 18 to supply the enhanced light to the liquid crystal display panel 4.
The LED substrate 14, which is connected to the first printed circuit board 24, supplies the drive signal to the LEDs 12 corresponding to control signal from the first printed circuit board 24. The LED substrate 14 mounted with LEDs 12 is received and fixed in the mold frame 6. Additionally, the liquid crystal display panel 4 and backlight assembly 50 are fixed and supported in the mold frame 16.
The bottom chassis 22 is fixed to the mold frame 16 on the lower side thereof. An opening is formed in a portion of the bottom chassis 22 such that a light emitting display panel 30 may be inserted therein.
The second printed circuit board 26 is supplied with a drive signal from a drive circuit (not shown) located in the mobile phone side by a mobile phone connector 28. The mobile phone connector 28 is fixed to another connector attached to the drive circuit located in the mobile phone side to be supplied with the drive signal from the drive circuit in the mobile phone side. The second printed circuit board 26 supplied with the drive signal generates various control signals corresponding to the drive signal.
The first printed circuit board 24 is connected to the second printed circuit board 26 through a first pad unit 38 formed in the second printed circuit board 26. The first printed circuit board 24 is connected to the integrated circuit 6 of the liquid crystal display panel 4 and LED substrate 14 by a flexible printed circuit board (not shown). The first printed circuit board 24 connected to the integrated circuit 6 and LED substrate 14 drives the integrated circuit 6 and LED substrate 14 corresponding to the control signals supplied from the second printed circuit substrate 26.
The light emitting display panel 30 includes a first substrate 30a and a second substrate 30b. Organic LEDs (not shown) are arranged on the first substrate 30a in matrix form. Organic LEDs generate a predetermined amount of light corresponding to the amount of current supplied. The light emitting display panel 30 is connected to the second printed circuit board 26 by the second pad unit 36 of the flexible printed circuit board 32. An integrated circuit 34 is mounted on the flexible printed circuit board 32. The integrated circuit 34 lets the light emitting display panel 30 to display a predetermined image in response to the control signals supplied from the second printed circuit board 26.
However, the conventional portable display device 60 may allow light to leak into an undesired region. More specifically, since the light supplied from the backlight assembly 50 is emitted to the non-pixel regions of liquid crystal display panel 4, the light efficiency and the image quality of the conventional portable display device are deteriorated. In addition, as shown in FIG. 2, if debris P enters the backlight assembly 50 through a space between the liquid crystal display panel 4 and the mold frame 16, light is blocked and the image quality is further deteriorated. Further, conventional portable display devices 60 have relatively weak mold frames since the panel 4 is mounted to and supported by the mold frame 16.